Check your trusts uniform policy - some are stricter than others, but most people wear black trainers.
You're going to be on your feet all day everyday, so you want comfortable and hard wearing. I bought a pair of black Nike trainers that were on offer for £90 in 2020 (so probly about £150 in todays prices lol) and they're only just starting to wear out now. When it comes to footwear, you get what you pay for - buy cheap, buy twice!